DENVER (AP) – A total of 27,000 gallons of oil – the equivalent of about two storage tanks – have been spilled into the South Platte River from flood-damaged tanks as of Monday.

The latest spills are a 36 barrel release at a Noble Energy location between Evans and LaSalle and a 26 barrel spill at an Anadarko Petroleum site near Johnstown, the Colorado Oil and Gas Conservation Commission said.

About 1,300 wells remained shut down because of the flooding, down from 1,900 last week.

In its update, the commission said the spills would have to be cleaned up though it would be difficult to tie the spills to the different companies that had the releases since the spills have been swept away with the flood waters.

It wasn’t clear whether there was any cleanup still going on or what risk the spilled oil posed. The river is a major source of drinking water and agricultural water but the state health department says the millions of gallons of sewage dumped into the river from broken sewer pipes and waste treatment plants pose a bigger problem.

Joseph N. Ryan, a University of Colorado professor researching how to limit the natural gas industry’s impact on the environment and communities for the National Science Foundation, said some of his researchers are taking soil samples along the river looking for evidence of benzene, which is a carcinogen, and benzene compounds, left by the spilled oil. The final data won’t be ready for weeks, but he suspects it won’t reveal significant accumulations because of the amount of water that rushed down the foothills and onto the plains.

“My expectation is that we wouldn’t find anything that’s going to cause a lot of risk,” said Ryan, a professor in CU’s civil, environmental and architectural engineering department.

The spills happened in the booming Wattenberg Field. Soon after the flooding began, activists started posting photos of overturned tanks and flooded gas wells, but inspectors were only able to gain access to the sites Wednesday, five days after the flooding hit the area.

The industry says no hydraulic fracturing was going on when the flood hit, but activists are still concerned about open pits that may have held fracking fluid that could have been washed away. Regulators say it’s rare to use pits for fracking fluid in the Wattenberg Field.